Image Quality Evaluation for Brain Soft Tissue in Neuro -endovascular Treatment by Dose-reduction Mode of Dual-axis "Butterfly" Scan.

Background and purpose: Flat-panel cone-beam CT (CBCT) is essential for detecting hemorrhagic complications during neuroendovascular treatments. Despite its superior image quality and trajectory over conventional CBCT (Circular scan), dual-axis butterfly scan incurs a slightly higher radiation dose relative to conventional CBCT. This study evaluates the image quality in dose-reduction mode to uncover the appropriate radiation dose for the butterfly scan.

Materials and methods: We prospectively included patients who scheduled neuroendovascular treatment and performed conventional CBCT and dose-reduction mode of the butterfly scan. Two reduced radiation dose modes were utilized for the butterfly scan: medium-dose butterfly scan (70% of the original dose, 45 mGy) or low-dose butterfly scan (50% of the original dose, 30 mGy). The enrolled patients were assigned alternately to receive either the medium-or low-dose butterfly scan. We evaluated and compared artifacts, contrast, and discrimination of the corticomedullary junction between conventional CBCT and one of the dose-reduction modes of the butterfly scan, with a 5-point scale scoring system.

Results: Twenty patients were enrolled in each of the medium-and low-dose groups, totaling 40 patients. Compared to conventional CBCT, the medium-dose butterfly group exhibited reduced artifacts, enhanced contrast, and discriminated corticomedullary junction (except in the occipital lobe). While the low-dose butterfly group exhibited markedly reduced artifacts and improved contrast (except in the occipital lobe), a significant improvement in corticomedullary junction discrimination was unobserved.

Conclusions: Even with dose reduction, the specialized trajectory of the butterfly scan enables artifact reduction, contrast improvement, and enhanced corticomedullary junction discrimination. However, the impact of the reduced dose was more noticeable, particularly in the occipital region where susceptibility to bone interference resulted in decreased contrast and compromised corticomedullary junction discrimination.

Abbreviations: AVM=arteriovenous malformation, CBCT=cone-beam CT, CAS=carotid artery stenting, CTDI=CT dose index, DAVF=dural arteriovenous fistula, FD=flow diverter,PTAS=percutaneous transluminal angioplasty and stenting.